Actinium was independently discovered by French chemist André-Louis Debierne in 1899 and subsequently by Friedrich Otto Giesel in 1902. Debierne, who was not only a friend of Marie Curie and Pierre Curie, but also worked with them, discovered actinium while working with uranium oxide or uraninite, which is a major uranium ore.

Occurrence

Trace amounts of actinium are naturally found in very low concentrations in uranium ores as 227-Ac, its most stable and abundant isotope. It can also be synthetically produced by neutron irradiation of radon in a nuclear reactor.

Isotopes

27 radioisotopes have been identified. The three with the longest half-lives are:

227-Ac with a half life of 21.773 years, emitting both alpha and beta rays.

225-Ac with a half life of 10 days, and

226-Ac with a half life of 29.37 hours.

The remaining isotopes have much shorter half-lives ranging from less than 10 hours to less than a minute.

Electron shell configuration

1s2

2s2

2p6

3s2

3p6

3d10

4s2

4p6

4d10

4f14

5s2

5p6

5d10

6s2

6p6

6d1

7s2

Applications

Currently actinium has it has no commercial or industrial applications. However, because it is extremely radioactive (150 times more radioactive than radium), it is used to produce neutrons.